Why does the Xbox 360 have a lot of different game cases?

Some of them are like really flexible, while others aren't, and there seems to be like 5 different kinds of ';buttons'; to take the game out of the case. Why is this?Why does the Xbox 360 have a lot of different game cases?
Competition between different suppliers keep them on their toes and helps Microsoft reduce costs as it plays one supplier off another. Basic economics.